


Chemistry Lesson

by sushisama



Category: Gravity Falls
Genre: Human AU, M/M, PWP, Smut, bad chemistry pick up lines, professor!Dipper, professor/student, student!Bill
Language: English
Status: Completed
Published: 2016-09-15
Updated: 2016-09-15
Packaged: 2018-08-15 04:46:24
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 6,203
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8043091
Author URL: https://archiveofourown.org/users/sushisama/pseuds/sushisama
Summary: Alone in the lecture hall, Professor Pines is approached by one of his students…





	Chemistry Lesson

**Author's Note:**

> This was based off a prompt that I found. Nothing more than a smut, not meant to be thoughtful or anything. Just sexy fun times.

            Dipper Pines found himself in front of the dry erase board of his assigned lecture hall in the early Friday evening.  He wasn't really that upset with the situation, though: it wasn't like he had anything better to do.  He was states away from his family and former friends, and the new professor of chemistry had no one to really spend time with on his recent campus.  And for the most part, that suited his introverted nature just fine.

            He had taken a pause in grading homework to work on some formulas he had been postulating.  All he could do was work on the board; saving anything he would do in the laboratory for another day when he wasn't trying to be the example teacher.  He also figured that if he got all the homework down that evening, no matter how long into the night it took, it gave him the weekend to work on his newest thesis.  Working so hard was the only thing he could surmise would get him closer to tenure without having to be there for twenty years first.

            He had lost track of time, only using the dying light outside the windows of the far side of the room as a clock.  He knew he had been on this problem for a lengthy amount of time, but he wanted to finish his line of thinking before he went back to his grading.

            And also to forget about the post-it note stuck to the paper on the top of the pile, which had been the cause of his most recent pause.

            Dipper stood back from the board, looking between formulas and his hypothesis, to make sure everything fit.  After a long moment, his eyes lit up as he went over a particular spot, and a thought came to him to solve one of his small hiccups.  He stepped forward to fill in a specific equation, but in his eagerness, he hit the board too hard and dropped his marker.  With a hushed expletive, he leant down to pick it up.

            "What a great view."

            A chill went up Dipper's spine at the smooth tone.  Without retrieving the marker, he snapped up and turned around.  His wariness was not eased as he laid eyes on the copper-toned man with blond/black hair, who was leaning against his desk.

            "Mister Cipher," Dipper uttered, more out of surprise than acknowledgement.

            The student grinned, his golden eyes shining with mischief.  "Professor Pines," he called back. 

His arms were crossed in front of him, but Dipper knew what was beneath.  He knew about the taut chest and slim figure that boasted both health and strength.  And he knew it from the tight shirts he wore, the way he stretched and put his arms behind him, knowing full well he was showing off his form.

Dipper coughed and turned his back to him, knowing he couldn't hide the blush that covered his pale and freckled cheeks.  He quickly retrieved the marker from the ground and went back to finishing his thought on the board.

"What are you doing here, Mister Cipher?" he asked.  He was desperately trying to focus on anything but the skinny jeans his student was wearing.  "Shouldn't you be skulking around some parties at the dorms?"

He chuckled.  "That only has so much entertainment to it.  Besides," he could hear paper rustling, "I wanted to make sure you got my note."

Dipper had.  And when he chanced a look at the taller male, he saw the post-it in his hand.  He narrowed his brow a little, not really wanting to discuss it.  Not that he had even understood it, the phrase on it had been vague at best, but it wasn't the first post-it he had gotten from his student. 

Ever since the first day of the semester, William Cipher had been in the front row, smirking at him.  But that had been the tamest from him.  He leered, made subtle gestures, left the notes, and had more than once stayed after class just to insinuate that they should spend some time alone. 

The worst part of it all was that Dipper had found himself under the spell of the youth's charm, under his smooth voice and magnificent physique.  And were the situation any different, Dipper would eagerly take the chance with such a fine specimen.  But he was still a professor, and he was still a student.  The line had to be drawn, and he had to stay behind it.

"I'm not sure where you were going with the request, Mister Cipher," Dipper started, his attention back on the board, though he was unable to focus, "but I'm sure it was inappropriate."

"You can call me Bill, you know," he said.  Suddenly, he was next to Dipper, far too close for comfort, as he could feel his heat.  He picked up a marker from in front of the board.  "And I'm pretty sure you have what I'm looking for."

"I don't have any Uranium," Dipper retorted.  His hazel eyes narrowed at what Bill was starting to write, and where he was writing it.  He should have been concentrating on the four lines he made, but he was more grateful that he hadn't erased anything he had been working on.

"But I've got the others, that's the only one I have left."

Dipper sighed, rolling his eyes.  He squeezed the bridge of his nose, and then gave his attention fully to Bill.  He wanted him to leave, to get out of the classroom and leave him alone, before any of his thoughts went the way the student was trying to lead them.  But he had a feeling that if he didn't play along, he wouldn't get him to go any sooner.

"And what are the others?"

He hated that perfect smile he returned with.

"Well, I've already got the fluorine," he said, writing an 'F' over the first line.  "As well as the carbon..."  He marked in a 'C' on the third line.  "And then there's potassium..."

Dipper grabbed at his wrist before he could finish with the 'K'.  His face was red, he knew, but he had to put a stop to this.  Bill didn't resist, just grinning at him.

"S-stop," Dipper insisted, though hesitant.  "You should leave, Mister Cipher."

"Bill," he reiterated.  He turned fully to Dipper, putting a hand on top of the one on his wrist.  "Is that really what you want?"

Dipper stammered.  He had always been good at keeping Bill at a distance, to make it seem like he wasn't interested while also trying to stave off his own temptation.  But now he was close, so close he could feel his heat, smell his had-to-be-expensive cologne, and be within his intense stare.

Dipper pulled his hand away, taking several steps back.  "Look, I'm flattered, trust me, I am," he said, his words coming out quickly, "but I just, look, I just can't-"

"Why not?"  Bill was stepping closer, moving in on him in a way that backed him against the board.  "You stare, you know.  I see you."

Dipper felt he was on fire.  Bill had successfully gotten him trapped, hands on either side of his shoulders.  He wanted out, wanted away from this situation, wanted away from the attractive student smiling at him, because he wasn't sure if his conviction would hold.

Of course he had stared; Bill had made it impossible for him not to.  He was always in the front row, wearing something flattering, moving all the time so Dipper had to focus on him.  And he hadn't missed the vulgar gestures made at him, from the winks to the blown kisses, to even motions with his hands and mouth of things they could do together.

"You've thought about it..."  Bill's leg slid in between his, his thigh coming into contact with a vulnerable area.  He leaned in, his lips close to Dipper's ear.  "...haven't you?"

A shudder went down Dipper's spine.  He remembered the post-it notes that Bill had left on every paper he turned in, all with mounting amounts of lewd comments and suggestions.  Most of them had been hidden in bad chemistry jokes, but there had been a handful of them that had outright suggested they engage in sexual contact.

He could still remember the thoughts in his head when Bill had wrote out simply what he wanted to do with his mouth.

Dipper pushed away at Bill's chest, though it was a half-hearted attempt to get him away.  "It... it doesn't matter," he said.  "You're still my student, I'm still your teacher, we can't-"

"Why not?" Bill interrupted with the same question.

"Mister Cipher-"

"Bill."

"Bi- No, Mister Cipher," he weakly asserted.  "I know this seems easy to you, but ethics and all-"

"This is chemistry," Bill said, moving until his chest bumped against Dipper's, "not philosophy."

"That's more of an English thing, actually, philosophy is more-"

Dipper was interrupted by a pair of lips on his, in a sudden and harsh kiss.  At first, he did nothing, his eyes wide and staring into Bill's, who seemed to have his grin in those golden orbs.  When he didn't seem to disapprove, Bill pushed forward, his lips almost crushing Dipper's, his leg moving further to rub against him, and his palms coming to claim the sides of his face.

And for a moment, he wasn't sure if he was kissing back or not.  His thoughts had fuzz around them, warm like the heat Bill was giving off.  His hands were still on his chest, a moment ago pushing him away, but now tightening on the all too thin cotton.

Bill was the first one to pull away, his grin from almost ear to ear.  "Was that so horrible?"

Dipper was quiet at first, his head still leaning forward toward Bill, and he would be lying if he wasn't the bit saddened by the lack of the surprisingly chapped lips on his.  He blinked, his nerves still on fire from the action.  However, he shook his head, and once more pushed at him.  "We can't..."

Bill's brow furrowed lightly.  "You know I'm twenty-one, right?"  He sighed a little.  "I'm an adult, you're an adult, if we're both consenting, who cares?"

"You keep glancing over the teacher/student thing."

"But that's your only hang up, right?"  Bill's thumb was moving along his jaw, a gentle motion that Dipper couldn't help but move into.  The professor nodded unwittingly into his palm.  "Then there shouldn't be a problem."

"Still-"

"What's my grade currently in this class?"

"Okay, that's not the point."

"It kind of is, isn't it?"  A hand trailed down his body, resting on his hip.  "I'm clearly in no need of help with that.  And it's not like you used your position to assert yourself over me."  He snickered.  "Not like anyone would think you could assert yourself on anyone, really."

Dipper narrowed his brows.  "Hey, I am very capable of-"

"-waiting for someone to make the first move?"

He glared at him, face still red.

"Now that that's all cleared up..."  Bill leaned in again.

"Bi-Bill, we really shouldn't..."

"Shh, professor," he whispered, his breath ghosting over his lips.  "You think too much."

He kissed him again, and Dipper could not find the will to resist.  He kissed back this time, more aware of his role in the scenario.  His hands tightened again in his shirt, and Bill took advantage of this obvious wavering in conviction.  He could feel his tongue flitting over his lips and teeth, and opened his mouth to let him in.

As the kiss deepened, Bill's hold on him grew bolder.  The hand at his hip was now under his sweater, the other turning his head to allow better access.  His leg moved more, his thigh rubbing against him in a rhythmic motion.  He moaned into Bill's mouth, which was returned with a chuckle.

Dipper, despite himself, was moving into Bill's body.  Any part of his mind that had tried to reason away why they shouldn't be doing this was silenced as Bill pulled away to start nipping at his jaw and neck.  He moved to cling to his shoulders, turning his head and letting him have more access.

"Wait, wait, Bill," Dipper spoke up, though he didn't make any moves to push him away.

Bill stopped, turning and moving so he could look Dipper in the eyes.  "What?  Are you still on about the ethics or whatever?"

Dipper shook his head.  He could say the words, but the truth was, at this point, he knew he had lost his battle of will.  With his erection pressing hard against Bill's though, there was no denying that he had the same thoughts as Bill.  No, he was sure what was going to happen at this point, and he no longer cared about the truth, in fact he was on the verge of welcoming it.  But if he was going to go through with it, they had to be careful.

"We shouldn't, I mean," he stammered, "not here.  What if someone-"

"You are literally the only teacher that stays this late on a Friday night," Bill spoke up.  "And it's a game night, so everyone else is either at the field or somewhere getting shit faced."

"Well, still, maybe we should, um, go somewhere else?"

Bill snickered.  He gave Dipper a peck on the lips before saying, "I have been thinking of fucking you here for fair too long to just go somewhere else."

If Dipper had been flustered before, that comment must have made his face go purple.  "You... how long..."

"Since the first day of class," Bill answered the vague question.  "And I know you've thought about it, too."

"I..."  Dipper didn't even know how to start.  He had thought about it, of course, but he didn't think it was to the extent Bill had been thinking about him.

Bill raised a suggestive brow.  "What all did you think about?"

"Bill, this isn't really...  I don't know..."

"Don't know how to say what you want?"

"Well, I guess, or maybe..."  He didn't know how to say it.  He considered the words in his head vulgar, things he didn't know how to say out loud without blushing.

Bill leaned in toward his ear again, saying in a low tone, "Then why don't I tell you what I think of?"

Dipper felt a chill go up him.

"I think of you on your knees," he whispered, his voice sultry in tone.  "With my co-"

"Stop," Dipper halted, putting a hand over his mouth.  He couldn't look him in the eyes, knowing full well what the next thing Bill was going to say.

Bill moved his head to be able to talk.  "Well, hey, you don't have to; I'm just saying, a blow jo-"

"No, that's not it," Dipper said.  "That kind of... I like doing that, I just..."

"You like doing it, huh?" Bill said through a chuckle.

Dipper huffed, turning his gaze away again.  "S-shut up."

"But you don't like talking about it?"

He didn't answer, his cheeks still aflame.

"God, that's hot."

Dipper pushed away at him.  "Stop making fun of me."

Bill was still chuckling, but it was good natured.  "I'm not; I like that about you..."  He took Dipper's hand.  "You got that whole innocent thing going on.  But are you really?"

"I've had sex, if that's what you're asking," Dipper replied.  He didn't pull his hand away, but was curious what Bill was doing as he moved it.

"I figured you had," Bill said.  "And I bet a lot, too.  But I wonder..."  He settled Dipper's hand at its ultimate destination.  "...how good were they?"

Dipper's eyes widened.  Bill had put his hand between his legs to feel his student's growing length.  It was thick, he could feel that, but it was still...

"That's half mast," Bill announced, smirking.

Dipper was looking away again, not willing to let Bill see the effect of that fact was having on him.

Bill left his hand there, moving his fingers to gently stroke through Dipper's hair.  He kissed the side of Dipper's face.  "About what I was trying to say earlier..."

Dipper looked back at him.  "You've thought about it?" he asked with a slight hesitance.  In a forward move, he ran the base of his palm up the clothed erection, earning him a low murmur from Bill.  His student nodded with some eagerness, losing a little bit of his smoothness.  Dipper had to smile at the chit in his persona.  He was only about five years older than human, but there was still something nice about being able to make him swoon, even a bit.

Dipper kissed him gently, rubbing him as he did.  He could feel Bill's smile as he kissed back, and the length growing under his palm.  He pulled away to smile at him before his eyes flicked down.  Just as Bill started to push on his scalp, Dipper was bending his knees before him.

As Dipper descended, he unzipped Bill's jeans.  He put his hand inside the denim, not surprised that he didn't have any underwear on.  He rubbed at the stiff flesh for only a moment before freeing it completely.  His eyes were fixed on it for a long moment, especially on the tip. 

"Like it?" Bill asked.  His hand was running through Dipper's hair.

Dipper's eyes didn't leave the glint of metal in front of him as he said, "It's just... new."

Bill snickered.  He pushed on the back of his head lightly, and Dipper let himself be led.  He opened his mouth, taking the tip between his lips.  He licked along the head, tasting the metal along with the dots of precum.  He looked up at Bill as he went down, his tongue on the underside of the shaft.

Bill was looking at him intently, biting his lip as he met Dipper's gaze.  He didn't say anything, just watched as he took further of his length into his mouth.  His fingers were tangled into his brunet curls, but he wasn't pushing him anymore.  He was letting Dipper set the pace as he got half way down his member and made his way back up.

Dipper couldn't take the whole thing in his mouth, no matter how he relaxed his throat.  He was able to get half of it before he started to gag, so he settled for moving along as much of the shaft as he could comfortably.  Bill was urging him on a little, but it was more in speed than how far down to go.  His other hand was on his shoulder, his fingers curling in lightly.

Dipper had a hand on his hip, and brought the other to the base of Bill's penis.  He moved it in time with his mouth, meeting his lips half way up before stroking back down as his lips went over the tip and his tongue licked at his piercing.  He let his teeth grace down the length, and he received a shudder from the other male.

"Gods, you are good at this..."

Dipper had to smile around the flesh in his mouth.  He was pleased by the way Bill was starting to lose all that composure he carried with him.  He could even tell where Bill was wanting to pull his hair more, to make him go faster and deeper, but he was doing what he could not to, even keeping his hips from bucking forward into his mouth.  His head was leaned back, his mouth open with wordless sounds with each take of his length Dipper made.

"Professor," he called, his eyes coming back to look at Dipper.  "You're still hard, aren't you?"

He faltered for a moment, stuttering around him.  He was almost painfully hard at this point, his erection straining at his khakis.  He had been hard since their make-out session, with Bill deliberately trying to get him wild rubbing up against him.

After nodding, Bill went on, "You should touch yourself then."

Dipper was sure his face had never been so red than this whole event.  Despite his embarrassment, though, he took his hand from Bill's hip to unzip his own trousers.  He pulled his erection from his boxers and pants, and almost instantly started to stroke in time with his other hand.  As he did, he moaned against the length still in his mouth, which in turn got a long groan from Bill.

For some long moments, the only sounds in the lecture hall were the labour of Dipper's actions and Bill's heavy breathing, with the occasion click of metal against his teeth.  Bill would make some vulgar remark here and again, but otherwise, his suave comments were gone in favour of being pleasured.

"Keep going," Bill urged.  He bucked his hips forward, and it took an effort on Dipper's part not to be gagged.  He pulled away some, but Bill's hand kept him in place.  "Don't stop, I'm almost there."

Dipper's action stuttered for a breath.  He pulled away for a moment, his hands still making work of the different lengths in their palms as he looked up at Bill.  "What do you-?"

"I want to come in your mouth," Bill said easily.  His eyes still softened, though, as he asked, "Is that all right?"

 _Better than on my face,_ Dipper thought.  "It's okay, I don't mind," Dipper assured.  "Just tell me when, okay?"

Bill nodded.  Dipper put his mouth back to work, and for a few more minutes, it was like before, all quiet aside from breath and the sounds from Dipper's mouth.  He had been close himself, from all of Bill's teasing, and he had a slightly rougher and faster pace for himself to try and go when Bill did.

"F-fuck, there," Bill muttered out, pulling on Dipper's hair.  "I'm coming, I'm..."

Dipper moved to the head, and he bit around it gently, his tongue gracing the metal at the tip.  Bill's fingers tightened in his locks, holding his head in place as he spilt his seed into his mouth.  Dipper squeezed at the base, stroking it just so as he gulped up the ejaculate.  He swallowed as it came, almost greedily.  He hadn't lied when he mentioned he liked doing this, it was just something he had never felt a need to announce.  But he was willing to show it as just feeling the substance go down his throat sent him over the edge, and he stained the wooden floor as he came hard.

When he felt nothing more coming, he slumped back, resting on his rear as he panted, his member still hanging out of his pants and wilting.  He used the back of his hand to wipe at the bit that had drippled out of the side of his mouth.  He was staring at the stain on the floor, his mind in a whirlwind of sensation and realisation.

Before he could mention anything of what happened, Bill was leaning down, dabbing at the mess with a handkerchief.  His golden eyes met Dipper's, and the professor could just vaguely make out that he hadn't put his spent member away.

"We aren't done, you know," Bill said calmly, all of his suave attitude back.

"W-what?" Dipper stammered out.

There was a chuckle.  Bill leaned forward, holding onto Dipper's shoulders as he gave him an almost bruising kiss.  Dipper didn't respond at first, but when he felt Bill's tongue, he obliged and opened his mouth.  Bill's arms moved to his thighs, and Dipper got the hint when he was moving him to wrap around his hips.  Bill held him around the middle, lifting him up as he stood, his mouth still clamped around Dipper's.

He moved them the short distance to the desk, laying Dipper across the wood.  It was just wide enough that only his body was against the grain, his legs still wrapped around Bill's waist.  He broke the kiss for only a moment to adjust them before he came back for more.

Dipper grabbed at his shirt, keeping him close as their lips continued at each other.  It was a few long moments before they each pulled away, breathing hard.  Bill started to bite and nip at his jaw and neck.  Dipper turned his head, letting him access as light sounds left him.  His hands were wandering around Dipper's shirt, ghosting over his sides and causing him to shudder.

"You really want to-?"

Bill didn't even look up, kissing at his chin.  "Didn't you want me to fuck you?"

Dipper blushed.  "But we just-"

"I know you're a professor and all," Bill said, kissing over Dipper's face, "but you're not that old."

"I need a moment," Dipper replied.  He inhaled sharply at a harsh bite to his jaw.

"So do I," Bill answered. 

He returned to kissing him, and Dipper got more involved with his lips than worrying about stamina.  They were lost in the moment, enjoying teeth and tongue, and he lost track of time as Bill leaned against him, their bodies in close contact.  Bill rubbed against him, though neither of them was ready to go again quite yet.

Bill pulled up his shirt at some point, exposing his stomach.  He left the kiss to start pressing his lips against his abdomen, circling his belly button with his tongue.  Dipper arced when he felt the lightly moist muscle dip into his naval.  His fingers tangled into his hair, desperate to cling to anything as Bill almost expertly explored his body with his mouth and hands.

Bill rose up for a moment to look Dipper in the eyes.  He kissed him briefly before pulling away, and lifting up Dipper's shirt.  He pulled the fabric just half way, though, leaving his eyes covered and his arms loosely bound.  He struggled for a moment to take it off, but Bill stopped him with gentle pressure to his wrists.

"Keep it there," he said low, lips close to Dipper's again.

"Bill, what-"

"Give it a shot," he interrupted.  His lips were on his jaw again.  "It makes things... different."

Dipper nodded, and didn't move more than to make himself as comfortable as he could with part of him still leaned over the desk.

He gasped at teeth right beneath his chin.  It was the hardest bite he had received so far, and he knew it was going to leave a mark.  "Wait, stop."

"Who's going to know?" Bill answered.  He moved down, his next bite at the junction of his neck and shoulder.  It was rough, and he sucked at the area, and there was no doubt the mark it would leave.  "But I want you to know."  He licked over the area.  "I want you to remember this..."

Dipper was breathing heavily as Bill was going down his body once more.  It had been different before, when they first started, he had felt some semblance of control over the situation he really had no handle on.  But now he was laid out, exposed even further as Bill was simultaneously removing his pants, and he felt naked in more than the literal sense.  He didn't know the look in those golden eyes, if they were approving or disgusted by him, and he didn't want to know in the same amounts that he did.

"You know, you were hot with your clothes on..."  Dipper bit his lip, anticipating the rejection of his body.  He knew he wasn't the handsome specimen that Bill was, but he didn't want to hear it from him.  "But this, you're just..."  He kissed his love handles, making it clear he saw the weight Dipper had put on through poor diet and lack of time to exercise.

"I know I'm fat," Dipper finished for him.

"I would go with chubby," Bill corrected.  He kissed the expanse that was his lower belly to his hips.

"Shut up."

Dipper shuddered when he chuckled against his skin.  "I like it."

"Don't lie," Dipper said, his tone bitter.  He had heard the line before, all to get into his pants.  Not that Bill needed to do that, as evident by his khakis on the floor. 

"I'm not," Bill assured.  He took hold of Dipper's thighs, moving his legs until his ankles were on Bill's shoulders.  Dipper could only guess what was coming next, relying on the feel of his hands and mouth against his skin, still not attempting to take off his makeshift blindfold.

Bill took a hold of his member, which was half-way back to life.  He stroked lightly, working on getting it full again.  "It makes sense for you, you'd look weird skinny."

Dipper didn't respond, instead making an odd whine when Bill was no longer touching him.  "Besides, I'm sick of what people call pretty..."  There was some rustling of fabric, and he could hear a soft pop.  "All the guys I'm sure you'd imagine I've been fucking, they're only worth the ten minutes I give them."

A gasp left him as he felt something cold and gel like drip down his body, landing just above his entrance in a glob.  He shuddered when Bill swirled the goop around his entrance.  "You're more than that," he went on.  He prodded at the hole, the tip of his finger sinking in as he continued talking, "You're real, honest, it makes you hotter when you open your mouth, unlike them."

Dipper moaned as the digit dug into him until he felt Bill's hand.  "I've been thinking of fucking you for so long."  He started to move in and out of him.  "I could have had you in that first week, and don't even try to deny it."

He could vaguely hear another sound, something like flesh on flesh, but he was distracted from it when a second finger was inserted into him.  Bill started to pump both in and out, his pace picking up some and going a bit rougher.  He was only half listening to what he was saying, lost in the feeling of the digits moving, especially when he curled the tips as he got the whole way in.

"But I'm glad I waited."  He added a little more of the lubricant before sliding in a third finger.  "Glad that this isn't just a ten minute fuck like all those 'pretty boys'."  And then his hand was gone.  Dipper whimpered at the loss, and he pulled on Bill's shoulders with his ankles.

Bill chuckled.  He kissed the side of Dipper's foot.  "Don't you think it's better this way?"

"Yes, yes," Dipper said, his tone eager.  He still wasn't paying attention, more rapt on the idea of what was coming.  "Please, Bill."

The desk squeaked as Bill leaned forward, and Dipper could feel the metal of his piercing at his entrance.  "Aren't you glad you gave in?"

Dipper didn't care, he would tell him anything, and he just wanted him inside of him.  "Bill, stop teasing, just-"

"Say it, and I will," Bill commanded with a sultry tone.  "Say what you want me to do to you."

Dipper turned his head, biting at his arm, too embarrassed by the request.  "Please, just do it."

"Do what?"  The head was still just at his hole, just barely there.  Dipper tried to pull him forward with his feet again, but Bill simply took hold of his ankles, holding them outstretched.

"Don't make me..."

"I want to hear you say it," Bill said.  He was leaning back just a bit, and Dipper again whined when the contact was lost.  "I bet something nasty like that from you would just be so hot..."

"Are you like this with everyone you sleep with?" Dipper asked, though still faced toward his arm.

"I don't normally spend time talking."

"I figured hearing your own voice would help get you off," Dipper muttered, thinking of all the ramblings Bill had given him over the semester.

"Touché," Bill said through a chuckle.  "But if you want this dick, you're going to need to say it."

Dipper sighed.  He did want it; he was almost at the point of needing it.  Even if he couldn't say it out loud, he had been thinking of it as long as Bill, and the long wait both had frustrated him and was to their benefit.  It did feel right; it did feel like this mounting tension made this moment so much better.

Finally, Dipper turned to Bill, still unable to see him.  "Fuck me, Bill.  Please fuck me."

He could feel the chill that went through Bill.  Before he could make any sort of quip about it, though, Bill was leaning forward, and in one go, he was half way into him.  Dipper let out something like a scream, a mix of the pain from the suddenness and pleasure.  He had been properly stretched, so the sensation was more of being filled so quickly and the unusualness of the piercing against his insides.

"Say it again," Bill said through a shudder.  He was still holding his ankles to the side.

Dipper groaned at the realisation that there was more to go inside.  He didn't have to look, he just knew from what he had just taken into his mouth moments ago.  "Fuck me, don't stop."

Bill moved again, until he was fully seated into Dipper.  He let out a long moan as he filled him completely, his fingers curling into him.  "You feel so good," he murmured.  Dipper hissed as he started to move out of him.

"You..."  Dipper couldn't even finish the thought.  His words were swallowed up as Bill moved into him again, slow until just the last part, where he slammed into him.  He went with grunts and moans, inarticulate as it was, unable to say anything else as Bill started a rhythm.

Bill set his legs on his shoulders, bending over so he could give Dipper a bruising kiss as he continued to thrust into him.  They moaned into each other's mouths, mixing tongues and breath as the speed picked up.  Dipper forewent the shirt, shrugging it off so he could grab at Bill's shoulders.  He didn't seem to care, more concentrated at pounding into him.

"Tell me how you want it," Bill whispered.  "Tell me how you want me to fuck you." 

"H-harder," Dipper just barely got out.  "Do it... do it harder."

Bill grinned.  "Whatever you want, prof."  He accented the remark with a snap of his hips, and Dipper let out a loud yelp.  He covered his mouth in a thin attempt to quiet himself, but he couldn't help the sounds that came as Bill continued at the pace, slamming into him hard each time.  One especially loud expletive came when he was angled just right, and he hit his prostate, which had an added sensation with the bit of metal.

"Th-there, keeping doing that," he almost begged.  He moved against Bill's body, eager to meet him half-way for each thrust.

"You mean... this?"  Bill took hold of his backside and lifted him slightly, sliding his legs to wrap around his hips, creating an almost arched bridge as he angled himself.  He thrusted into Dipper once more, and he screamed out Bill's name.  Dipper held onto the desk as Bill continued, his head falling over the back as more noises left him.

"Yes, yes, yes," Dipper found himself repeating.  He could already feel the knot in the bottom of his stomach tightening.  He hated that he was close so soon, but it had been a while, and he had almost forgotten how good it felt.  "Are you... are you close?"

Bill nodded, not breaking his rhythm.  "Yeah.  You, too?"

Dipper nodded back.  "I want..."  He turned his head, not able to meet his eyes.

"Tell me," Bill egged on.   He was holding onto his hips, still moving the body under him.

"...come in me," Dipper finished.

"Fuck, _yes_ ," Bill hissed.  At the request, he picked up the pace, almost eager to finish.  He took hold of Dipper's member, stroking it with fervour.

That was enough for Dipper, and with one final arc and cry, he came on his stomach and Bill's hand.  It was only with a few more thrusts, and Bill was burying himself deep into Dipper as he spilled inside.  He groaned deep, but silenced it half way through with a rough kiss to Dipper's lips.  He could only return so much of it, but pulled away to breathe heavily.

Bill laid his head on Dipper's chest as he they both panted and tried to catch their breath.  There was a long moment of nothing but the heavily breathing.  Finally Bill moved, and Dipper sighed at the loss of the length inside of him.  He could feel Bill's seed leak out of him, and there was a vague consideration that he would need to clean that later.

"Hey... Prof..."

Dipper sighed, but it was contented.  He lazily looked at his student, a smile on his lips.  "What, Mister Cipher?"

Bill was grinning at him.  He was holding up the post-it note from before.  It had been stained by their exploits. 

"I got my Uranium."


End file.
